Technical Field
The present technology relates to transistors for high-efficiency power switching, and normally off operation.
Discussion of the Related Art
High-performance power switching devices are critical for energy-efficient power conversion. Such devices enable power switching products that may be used in the electrical systems of aircraft and automobiles.
High performance power switches require low on-resistance and normally-off operation. For III-nitride transistors, there is a tradeoff between low on-resistance and normally-off operation. Low channel resistance is typically achieved by fabricating an AlGaN/GaN heterojunction in which electrons transport at high mobility. However, electron accumulation occurs in the AlGaN/GaN heterojunction, resulting in a normally-on operation.
Prior examples of such transistors used a trench gate structure with a re-grown AlGaN layer on the sidewalls to create a high mobility channel. Such a design operates with low on-resistance; however, it also operates in normally-on mode, which can lead to unsafe operation in some applications.
A trench gate structure with a re-grown AlGaN layer on the sidewalls to create a high mobility channel is described by Okada et al. in, “Novel Vertical Heterojunction Field-Effect Transistors with Re-grown AlGaN/GaN Two-Dimensional Electron Gas Channels on GaN Substrates,” Applied Physics Express, 2010. While this approach has the advantage of low on-resistance, it has the disadvantage of operating in normally-on mode.
An improved high performance power switch which can provide low on-resistance and operation in a normally-off mode is desirable.